Throughout this patent, position designations such as “above,” “below,” “top” “forward,” “rear,” etc. are referenced to a firearm held in a normal firing position (i.e., pointed away from the shooter in a generally horizontal direction).
As used in this patent, “large caliber” denotes a rifle with a caliber or greatest case diameter of the cartridge of more than 15 mm. With large caliber rifles, a heavy projectile (for example, a bullet, an adapter base projectile, a charge of shot, a gas body or the like) is shot at a rather low speed compared with other, small caliber high-performance rifles. Consequently, the gas pressure is also comparatively low, particularly in the front region of the barrel.
In the case of a large caliber, gas-operated rifle whose cartridge diameter is above 15 mm, the breech is large and long, and hence heavy. As a result, the force required to reload it is also large. Since, as already mentioned, the gas pressure of such a rifle is low, the action area of the gas piston must be great. Accordingly the quantity of gas which is depleted from the barrel during firing is also large. For this reason, recoil-operated guns have usually been preferred. However, recoil-operated guns have the disadvantage of being particularly sensitive to the type of ammunition used.
In case of large caliber weapons, a central anchoring element upon which all occurring forces are supposed to impinge has recently been provided to save weight. To a large extent, when such a central anchoring element is employed, the weapon case can be designed in the lightest plastic style, since the weapon case is subjected to little stress because the stresses are largely absorbed by the central anchoring element. A gas piston which usually interacts with the gas cylinder requires an additional point of power input at the tapping point of the barrel. Consequently, it is rather heavy in construction.
Large caliber rifles are disadvantaged in that the rifle is built rather long, if it is constructed as an enlarged, normal caliber rifle.